The outdoor leisure activities are the best and most popular way to relax tension from busy weekday work. People can always enjoy their leisure time from outdoor activities, such as picnic, camping, barbecue, etc. However long time and over solarization during outdoor activities makes ones intolerable, not only the skin will become swarthy, but also ones may get sunstruck from ultraviolet, or even suffer a heat exhaustion. Therefore, ones often employ a sunshade or umbrella to avoid exposure to direct sunlight. However, the radiating angle of the sun shifts during times, and the conventional umbrella cannot meet the need.
Referring to a prior art “Improved Angle-Adjusting Structure of Crank-Hanging Umbrella” of Taiwan Patent published No. 485769, the angle-adjusting structure of this prior art comprises a cylindrical housing and a tilt-fixing mechanism disposed inside the housing. The canopy-supporting arm is engaged fixedly with the angle-adjusting portion. The direction-shifting part, which is in the lower part of the angle-adjusting portion, undertakes direction-shifting function inside the housing, and the canopy-supporting arm changes its angle responsively, and thus the shielding range of the canopy is adjusted. The displacement element of the tilt-fixing mechanism is screwed upward to press tightly the limiting element and fix the angle-adjusting portion, and thus the angle of the canopy is fixed. This prior art utilizes the direction-shifting part inside the housing to undertake angle adjustment. However the sphere diameter of the direction-shifting part is larger than that of the opening of the housing, thus there is always abrasion between the direction-shifting part and the opening of the housing, and the opening of the housing tends to be worn and deformed. Consequently, the direction-shifting part cannot be fixed firmly, and the angle adjustment of the crank-hanging umbrella cannot be performed.
Referring to another prior art published U.S. Pat. No. 5,937,882, the tilt-adjusting mechanism disclosed therein includes: a collar, slidably mounted along the mast, and pivotally connected to a supporting arm of the canopy, with the canopy tilting angle being adjusted through the sliding movement of the collar along the mast and the sequentially actuated movement of the supporting arm; and a plurality of positioning holes on the mast, with a selected one inserted through by a lock element to lock the position of the collar on the mast and determine the canopy tilt angle. As those positioning holes are disposed at a given interval, the canopy tilt angles are limited to those discrete positions of the positioning holes, and therefore the umbrella cannot shield all the solar radiation, which may come from any direction. One end of a connecting brace pivotally attaches at the top of the mast, and the other end pivotally connects to the supporting arm of the canopy. The mast has a winder, which utilizes a line passing through the umbrella to enable the canopy to open or close via a series of sequentially actuated movements of the interlinked elements. One end of the line is wound on the winder, and the other end passes through tubes of the mast and arm to connect with a knob immediately below the lower hub of the canopy. By turning the winder, the line is wound or released to enable the canopy to open or close. The path of the line begins from the winder, and then extends through the tube of the mast to a first pulley, and then extends downward outside the mast to pass over a second pulley carried by the collar, and then extends along a the tube of the arm to pass over a third pulley at the top of the canopy, and downward through a upper hub of the canopy to the lower hub, and then terminates below the lower hub. The line path between the first pulley and the second pulley is exposed to the environment, and to be easily worn, damaged, and finally broken, and then the umbrella cannot operate any more. Accordingly, life of the umbrella is shortened.